Various control devices have been heretofore developed which regulate the supply of fluid to a utility function such as a hydraulic actuator or the like. These devices operate on a pressure sensing basis, i.e. they sense a loss of pressure and close so as to block the continued flow of fluid into, and a loss of fluid from, the system through the leaking area.
Such prior art devices are found in the following U.S. Pat. Nos.:
U.S. Pat. No. 1,045,693--Gillman PA0 U.S. Pat. No. 2,426,212--Hedene PA0 U.S. Pat. No. 2,871,876--Edmund PA0 U.S. Pat. No. 3,295,420--Gleason et al PA0 U.S. Pat. No. 3,971,404--Quarve PA0 U.S. Pat. No. 4,080,987--Fogg PA0 U.S. Pat. No. 4,085,772--Roger PA0 U.S. Pat. No. 4,145,025--Bergeron PA0 U.S. Pat. No. 4,153,072--Thompson PA0 U.S. Pat. No. 4,173,233--Snyder